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- Kramarova, Tatiana V., et al.
(författare)
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Mitochondrial ATP synthase levels in brown adipose tissue are governed by the c-Fo subunit P1 isoform
- 2008
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Ingår i: The FASEB Journal. - : Wiley. - 0892-6638 .- 1530-6860. ; 22:1, s. 55-63
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Tidskriftsartikel (refereegranskat)abstract
- Despite the significance of mitochondrial ATP synthase for mammalian metabolism, the regulation of the amount of ATP synthase in mammalian systems is not understood. As brown adipose tissue mitochondria contain very low amounts of ATP synthase, relative to respiratory chain components, they constitute a physiological system that allows for examination of the control of ATP synthase assembly. To examine the role of the expression of the P1-isoform of the c-F-o subunit in the biogenesis of ATP synthase, we made transgenic mice that express the P1-c subunit isoform under the promoter of the brown adipose tissue-specific protein UCP1. In the resulting UCP1p1 transgenic mice, total P1-c subunit mRNA levels were increased; mRNA levels of other F1F(o)-ATPase subunits were unchanged. In isolated brown-fat mitochondria, protein levels of the total c-Fo subunit were increased. Remarkably, protein levels of ATP synthase subunits that are part of the F-1-ATPase complex were also increased, as was the entire Complex V. Increased ATPase and ATP synthase activities demonstrated an increased functional activity of the F1Fo-ATPase. Thus, the levels of the c-F-o subunit P1-isoform are crucial for defining the final content of the ATP synthase in brown adipose tissue. The level of c-F-o subunit may be a determining factor for F1Fo-ATPase assembly in all higher eukaryotes.-Kramarova, T. V., Shabalina, I. G., Andersson, U., Westerberg, R., Carlberg, I., Houstek, J., Nedergaard, J., Cannon, B. Mitochondrial ATP synthase levels in brown adipose tissue are governed by the c-F-o subunit P1 isoform.
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| 3. |
- Shabalina, Irina G., et al.
(författare)
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Leydig cell steroidogenesis unexpectedly escapes mitochondrial dysfunction in prematurely aging mice
- 2015
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Ingår i: The FASEB Journal. - : Wiley. - 0892-6638 .- 1530-6860. ; 29:8, s. 3274-3286
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Tidskriftsartikel (refereegranskat)abstract
- Point mutations and deletions of mitochondrial DNA (mtDNA) accumulate in tissues during aging in animals and humans and are the basis for mitochondrial diseases. Testosterone synthesis occurs in the mitochondria of Leydig cells. Mitochondrial dysfunction (as induced here experimentally in mtDNA mutator mice that carry a proofreading-deficient form of mtDNA polymerase gamma, leading to mitochondrial dysfunction in all cells types so far studied) would therefore be expected to lead to low testosterone levels. Although mtDNA mutator mice showed a dramatic reduction in testicle weight (only 15% remaining) and similar decreases in number of spermatozoa, testosterone levels in mt DNA mutator mice were unexpectedly fully unchanged. Leydig cell did not escape mitochondrial damage (only 20% of complex I and complex IV remaining) and did show high levels of reactive oxygen species (ROS) production (>5-fold increased), and permeabilized cells demonstrated absence of normal mitochondrial function. Nevertheless, within intact cells, mitochondrial membrane potential remained high, and testosterone production was maintained. This implies development of a compensatory mechanism. A rescuing mechanism involving electronsfrom the pentose phosphate pathway transferred via a 3-fold up-regulated cytochrome b5 to cytochrome c, allowing for mitochondrial energization, is suggested. Thus, the Leydig cells escape mitochondrial dysfunction via a unique rescue pathway. Such a pathway, bypassing respiratory chain dysfunction, may be of relevance with regard to mitochondrial disease therapy and to managing ageing in general.
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